Outdoor used C-type light bulb series consist of a plurality of miniature light bulb sockets connected by electrical wires and completed with a rear light bulb socket (1) at the end of the electrical wire. The socket (1) has a groove (11) as shown in FIGS. 1 to 3. An electrical wire (2) extends into the socket (1) with its bent end further extending into the groove (11). A cover (3) is placed on the top of the socket to secure the electrical wire in position. The major disadvantage of the conventional structure is the lack of drainage means in the closed space defined by the wall of the socket (1) and the light bulb (4). Because rain water may penetrate into the interior of the socket when the light bulb socket is used outdoors, excessive water may lead to short-circuit, resulting in the damage of the light bulb series. Thus it is desirable to have an improvement made on the conventional structure.
In view of the above problem, the present invention is to provide a safe rear bulb socket structure used for a C-type light bulb series, in which the conventional disadvantage has been eliminated. Now the features and benefits of the invention will be described below in more detail with reference to the accompanying drawings.